The present invention relates to an electroplating apparatus for depositing a plated film on a substrate such as semiconductor wafer, and in particular to a plating apparatus which is capable for producing a plated film of uniform thickness.
In recent years, electroplating methods have been adopted for filling the fine trenches and holes, fabricated on an object such as semiconductor wafer, with metallic plating such as copper to provide circuit interconnections. One such conventional plating apparatus is known as a facedown type plating apparatus. FIG. 1 illustrates basic layout of this apparatus 10 comprised by: a plating vessel 101; an object 12 to be plated whose surface to be plated is placed face-down in the upper region of the plating vessel 101; a plating solution Q; a solution storage tank 103; a circulation pump 104 for ejecting the plating solution Q from the bottom of the plating vessel 101 through a plating solution supply pipe 105 at right angles towards the plating surface of the substrate 12.
Plating solution Q overflowing from the plating vessel 101 is collected in the solution recovery trough 106. A specific voltage is applied between the anode 107 and the plating jig 11 fastening the substrate 12 to serve as the cathode, so that the plating current flows between the anode 107 and the substrate 12 to form a plated film on the plating surface.
FIG. 2 is a cross sectional view of a portion of the feeding section of the plating jig 11.
As shown in this diagram, the plating jig 11 fastening the substrate 12 such as semiconductor wafer is placed opposite to the anode 107 in the plating vessel 10 containing the plating solution Q. A direct current voltage is applied between the plating jig 11 and the anode 13 by the plating power supply 14 for flowing plating current to form a plated film on the substrate 12.
Plating jig 11 has a feeding section which has feeding contacts 15 to contact the conductive part of the plating surface of the substrate 12, and when the contact points and the plating power supply are electrically connected, plating current flows from the plating power supply via the anode, the substrate and the contact points.
As shown in the diagram, the plating feeding section is comprised of a ring frame 17 which has a ring packing 18 on the inner periphery thereof and a feeding ring 19 which has a series of feeding contacts (or contact points) 15 spaced at a given distance along the periphery of the ring 19. The ring 19 and contacts 15 are located at the inside of the ring packing 18. The tip of the feeding contact 15 touches outer periphery of the substrate 12 where a conductive layer(not shown) is formed thereon. Then electrical contact between the conductive layer to be plated and the feeding contact 15 is formed. The tip of the packing 18 is pressed against the surface of the substrate 12 to form a tight seal so as to prevent the plating solution from entering into the inside of the packing 18. Therefore, the feeding contact 15 and the feeding ring 19 are prevented from being exposed to the plating solution.
FIGS. 3 and 4 show the conventional arrangement of feeding contact 15 attached on the feeding ring 19, respectively. In FIG. 3, feeding contacts 15 are provided at certain spacing on the feeding ring 19. While in FIG. 4, the feeding ring 19 is divided by insulators 20 into a plurality of electrically isolated sections (four sections in the example) and the feeding contacts 15 are attached to each of the divided sections of the feeding ring 19.
As shown in FIG. 3, according to the arrangement of a plurality of feeding contacts 15 attached on a common feeding ring 19, contact resistance of each feeding contact 15 varies from point to point, such that some of the feeding contacts 15 can pass current readily while others can not pass current easily. It cause a problem that plating thickness tends to be thinner at places nearby where those feeding contacts 15 can pass less current than other feeding contacts.
Also, as shown in FIG. 4, according to the arrangement of the feeding section 19 which is divided into a plurality of feeding sections separated by insulators 20 with feeding contacts 15 respectively, current in each feeding contact 15 can be controlled so that the differences of currents among the feeding contacts 15 can be minimized. However, the plating current is difficult to flow at the place between the feeding contacts 15 through the plating solution, resulting a problem that thinner plating thickness tends to be obtained in such regions of the plating surface.
The present invention is provided to solve the problems outlined above, so that an object of the present invention is to provide a plating apparatus having conduction detection means to enable detection of contact states (contact conditions) of the plurality of feeding contacts touching the substrate through the conduction detection sections so as to control the uniformity of the plating current flowing through the feeding contacts, and thereby obtaining uniform plating thickness on the substrate.
To achieve this object, there is provided an electroplating apparatus having a plating vessel for positioning an electrode in opposition to a substrate electrically affixed to a plating jig through a plurality of feeding contacts for impressing a specific voltage between the electrode and conductive layers provided on a plating surface of the substrate, thereby flowing a plating current from the electrode to the substrate through the feeding contacts so as to deposit a plated film on the substrate, wherein a feature is that a conduction detection device is provided to detect electrical conductivity properties between individual feeding contacts of the plating jig and the conductive layers on the substrate.
Also, it is preferable that the conduction detection device be provided with a plating current detection device to detect flow of electrical current through individual feeding contacts, so as to determine electrical conductivity of individual feeding contacts according to respective values of current flow detected by the plating current detection device.
Further, it is preferable that the conduction detection device be provided with a contact resistance measuring device to measure contact resistance between a conductive layer on the plating surface of the substrate and individual feeding contacts so as to determine electrical conductivity properties of respective feeding contacts according to respective values of contact resistance measured by the contact resistance measuring device.
Accordingly, because a conduction detection device is provided to determine electrical conductivity properties of each contact point of the plurality of feeding contacts, it is possible to confirm the state of conduction of plating current through each feeding contact, thereby eliminating one reason for producing non-uniform thickness of plated film.
Also, because the apparatus is provided with a plating current detection device and a plating current control device so that current flow through individual feeding contacts can be adjusted individually, it is possible to deposit a plated film of a uniform thickness on the plating surface of the substrate.
Also, in the electroplating apparatus of the present invention, each feeding contact may be made in a form of teeth contact to touch the conductive layer on the plating surface. Such a shape of the feeding contact enables to produce relatively uniform contact pressures on the conductive layers so as to generate uniform conduction states of electrical contacts, thereby enabling to deposit a uniform thickness of plated film in the vicinity of individual feeding contacts. Also, by adjusting the current flowing between the various contact points suitably, it is possible to obtain a uniform thickness of plated film over the entire plating surface of the substrate.